Fluid pressure controlled switch mechanism



Filed Dec. 19, 1947 Patented Nov. 11, 1952 FLUID PRESSURE CONTROLLED SWITCH MECHANISM Marcel Garanchcr, Chicago, Ill., assignor to Stewart-.Warner Corporation, Chicago, 111., a corporation of Virginia Application December 19, .1947, Serial No. 792,676

'2 Claims. 1

The present invention relates to compressors and more particularly to a control for a manually portable power operated air compressor which automatically stops the compressor when a predetermined pressure which may be varied is exceeded.

An object of the invention is the provision of an improved control means for afluid compressor for automatically discontinuing the operation of the compressor when a predetermined pressure is exceeded, which control means is readily adjustable to vary the pressure at which operation of the compressor is discontinued.

Other objects of the invention will become apparent from the following description wherein reference is had to the accompanying drawings in which:

Fig. 1 is a side elevational view of a portion of a portable air compressor with the improved control in; fragmentary section;

Fig. 2 is a fragmentary top plan View of the control by means of which operation of the compressor is regulated manually. This View may be considered as taken in the direction of the arrows on the line 33 of Fig. 1.

The control is substantially enclosed in a housing 582 which also encloses a, portion 44 of the air compressor, the latter being enclosed by a housing I90 which is secured to a motor housing 594. The casting 44 is provided with a socket projection I93 for a caster I 96 which projects through an opening 262 in the bottom of the housing I82. The compressor and motor assembly may also be supported by a pedestal 200 which may be generally U-shaped, and may be spot welded to the housing I94. The handle 204 may be spot welded to the housing I90.

The control means for stopping operation of the motor which drives the compressor whenever a predetermined pressure is exceeded at the discharge outlet 74 thereof, may be regulated manually to vary the pressure at which operation will be discontinued. Referring to Fig. 1 a passageway I24 is in communication with the discharge passage of the compressor and a diaphragm chamber I2 3 formed in a body casting 44.. The outer end of this chamber is closed by a bellows type diaphragm I28 having peripheral edges that are engaged between the edge of the opening in the body casting forming the outer end of the diaphragm chamber and a peripheral flange I30 on a tubular plunger housing I32 secured over this opening by means of a plurality of cap screws, one of which is shown at I34. These cap screws are threaded into openings in the casting and may be provided with lock washers so that the plunger housing and diaphragm will be firmly secured in position.

Slidable within the plunger housing I32 is a hollow plunger I35 which has a head adapted to be held in engagement with the outer side of the diaphragm I28 by a coil spring I38 reacting between the head of the plunger and a stop I40 carried adjacent the outer end of the plunger housing I32. This stop is provided with a fast thread such as the square thread shown which engages in a corresponding thread in the inner surface of the housing adjacent its outer end so that the stop may be adjusted longitudinally of the housing for varying the tension in the spring !33 and need be turned through only a relatively small angle to secure a large adjustment.

It is rotated for regulating the tension of the spring by means of a knob I42 having stem I44 operatively connected to the stop by any suitable means. This knob I42 projects through and is rotatably carried in a dial plate I46 set in an enlarged outer end flange I48 on the plunger housing I32. A C spring I50 is engaged in a peripheral groove on a reduced portion I52 of the knob extending through the dial plate I46 (Fig. 2) in a position to engage the back of the plate and thus hold the knob in position but yet allow free rotation of the same. The knob may be provided with an indicator I54 which sweeps over graduations I 56 on the dial for indicating, for example, air pressure in pounds per square inch at which operation of the compressor will automatically be discontinued if the indicator is moved to that point.

From the above description it will be apparent that deflection of the diaphragm I28, due to an increase in the pressure of the air in chamber I26, will force the plunger I36 outwardly in the plunger housing in opposition to the biasing force of spring I38. The magnitude of the pressure required to move the plunger can of course be adjusted by turning knob I 32, thereby advancing or retracting stop 14B and increasing or decreasing the tension in spring I38.

Movement of the plunger in this manner opens and closes a snap switch I58 of conventional construction through a semi-spherical abutment I carried adjacent the outer end of the plunger and projectin into a slot I62 in the wall of the plunger housing. The switch has a button or pin I64 for closing the same projecting into the path of the abutment, and this pin is depressed to close the switch when the abutment engages the same, as shown in Fig. l. Energiza-tion of the motor I 0 the underlying principles of the invention.

is controlled by the switch and as long as abutment I60 remains in contact with the pin I64, the motor circuit will be energized.

In order to permit manual control of the switch I 58, it is mounted so that it may be bodily oscillated to carry the pin I64 into and out of the path of movement of the abutment I60. As best seen in Fig. 1, an extended portion of the flange I36 on the plunger housing forms a base 66 to which the switch is secured by means of a shouldered screw I68 extending through the base and switch, and threaded into the inner end of a stem III) which projects through the outer end flange I 48 on the plunger housing. A washer 112 is interposed between the back of the switch and the base I66 and is engaged by the shoulder on the screw Hi8 so that the switch may be rocked to carry its pin into or out of the path of movement of the abutment IEO by manipulating the projecting end of stem I'IIl.

When the compressor is in use it is supported upon the floor by means of a caster I85 shown in Fig. l which is secured in a depending boss I98 on the bottom side of the compressor body casting M and a transversely extending foot 2% adjacent the rear end of the compressor. The foot may be made from a single strap of metal formed to provide a flat part for resting on the floor, and a pair of upwardly extending arms by means of which the foot is secured to the sides of the rear end section I96 of the housing by spot welding or other means of securement. The caster I 95 projects through an opening 232 in the bottom side of the forward section I82 of the housing so that it is in position to contact the floor and thus allow the compressor to be moved in the manner of a wheel barrow, or it may be carried by means of the handle 254.

In operating the compressor the manually adjustable knob I42 is first set at the pressure which it is desired to develop at the discharge end of the conduit 18. The stem IIIl may then be oscillated in the proper direction to move the pin I85 on the snap switch I58 into engagement with the abutment I58 on the plunger I3 5, thus energizing the motor and causing the compressor to be operated. The snap switch I58 is connected in the motor energizing circuit.

Some of the air discharged by the air compressorflows through passageway IZ i into the diaphragm chamber I25, and as the pressure in this chamber increases, it will finally reach the point where the diaphragm I28 is moved upwardly, from the position shown in Fig. 1, thus disengaging abutment I553 from pins I5 3 and allowing the snap switch I58 to open, thereby discontinuing operation of the motor. At any time it is desired the compressor can of course be shutdown by operating the stem III) to rock the snap switch body in a direction to move its pin I64 from the path of movement of the abutment I66 on the diaphragm plunger.

While I have shown and described a preferred embodiment of my invention, it will be apparent that numerous variations and modifications thereof may be made Without departing from I:

'4 therefore, desire, by the following claims, to include within the scope of the invention all such variations and modifications by which substantially the results of my invention may be obtained through the use of substantially the same or equivalent means.

I claim:

1. A fluid pressure operated control comprising body structure having a diaphragm chamber formed therein adapted to be connected to a source of fluid under pressure, diaphragm means in said chamber movable in response to variations in the pressure of the fluid in said chamber, means forming a cylinder opposite said dia-- phragm chamber, a plunger slidable in said cylin= der and adapted to be moved in one direction by said diaphragm means, means for biasing said plunger in opposition to said diaphragm means, a normally open switch having a projecting operating part and means on said plunger adapted to contact the operating part of said switch to close the latter when said plunger moves in response to a reduction in pressure in the chamber below a predetermined value, and manually op erable means for moving said switch bodily to a position at which said means on said plunger is ineffective to close the switch.

2. A fluid pressure operated control comprising body structure having a diaphragm chamber formed therein adapted to be connected to a source of fluid under pressure, diaphragm means in said chamber movable in response to variations in the pressure of the fluid in said chamber, means forming a cylinder opposite said diaphragm chamber, a plunger slidable in said cylinder and adapted to be moved in one direction by said diaphragm means, adjustable means in said cylinder for biasing said plunger in the opposite direction, a switch biased to open position having a projecting operating finger and a projecting part on said plunger adapted to contact said finger thereby to close the switch when said plunger moves in response to a reduction in pressure in said chamber below a predetermined value, and manually operable means for moving said switch bodily to remove said projecting ringer from the path of movement of said proecting plunger part thereby to render said finger an i 1said plunger part ineffective to close the SW1 0 MARCEL GARAN CHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Gilman, Sept. 25, 194.5 

